1. Field of the Invention
This invention relates to apparatus for making a yarn, comprising two juxtaposed, closely spaced apart twisting drums, which rotate in the same sense about parallel axes and at least one of which has a suction zone which faces the generally triangular twisting space defined between the twisting drums, and a fiber-guiding passage extending into said generally triangular twisting space at an oblique angle to the axes of said twisting drums and having an outlet opening which extends parallel to said axes and serves to supply fibers which are to be twisted together to form a yarn.
2. Description of the Prior Art
It is known that a yarn can be made in a process in which singled fibers are supplied through a fiber-guiding passage into a generally triangular twisting space between two twisting drums while a vacuum is applied through the peripheries of said drums to said triangular space so that the air is sucked from said fiber-guiding passage through said triangular space and the individual fibers are substantially parallelized by the air stream in the fiber-guiding passage. The twisting of the singled fibers will be improved if the singled fibers extend approximately in the direction in which the yarn is withdrawn. That orientation will be obtained if the fiber-guiding passage extends at an acute angle to the direction in which the yarn is withdrawn from the generally triangular twisting space either in the sense in which the fibers are supplied to said space or in the opposite sense. If the fibers are supplied to the triangular space through the fiber-guiding passage in the sense in which the yarn is withdrawn from said space, the opration can be described as forward twisting. If the fibers are supplied to said triangular space in a sense which is opposite to the direction in which the yarn is withdrawn from said space, the operation can be described as reverse twisting. In the latter case the fiber-guiding passage has relative to the direction of yarn withdrawal an inclination which is opposite to its inclination during forward twisting. Even though it is desired to orient the fibers approximately parallel to the line of yarn formation the yarns which consist of the fibers that have been twisted together do not always meet high requirements regarding strength and wear resistance and from that aspect it does not make a difference whether the yarn has been made by forward twisting or by reverse twisting.